Shallow water mine and arming means therefor



SHALLOW WATER MINE AND i MEANS THEREFOR Filed June 2, 1958, Ser. No.739,442 7 Claims. (Cl. 102-16) (Granted under Title 35, Us. (Iode(1952);scc. 266) The invention described herein may be manufactured andused by or for the Government of the United States of America forgovernmental purposes without the payment of any royalties thereon ortherefor.

This invention relates to a marine mine for use in shallow water andmore particularly to a shallow water mine which is armed by immersion inwater independently of the hydrostatic pressure applied thereto andwhich includes means for effecting self destruction of the mine in theevent that the mine is planted on the land.

In devices of this kind heretofore proposed it has been the usualpractice to discriminate between the impact received by the mine orcontact with water and the heavier impact of the mine when landing on aland target after being dropped from an aircraft in flight. Furthermore,such mines have usually employed hydrostatic pressure devices to actuatethe various control mechanisms of the mine when the mine is planted inthe Water. Such devices have been subject to the disadvantage that whenthe mine is planted in very shallow water, for example, there may beinsufiicient pressure to operate the hydrostatic devices thereof, andfurthermore, when launched in shallow water from an aircraft in flight,conditions may be such that it is impossible for the mine to distinguishby the shock received whether the mine is planted on land or in water.

The mine of the present invention does not rely upon the character ofthe shock received at the time of planting nor does it rely onhydrostatic pressure for its operation and for these reasons is free ofthe disadvantages which normally attend these prior art mines.

In accordance with the present invention the discriminating feature ofthe mine between water and land planting from an aircraft is achieved bya transducer element forming one arm of a balanced Wheatstone bridge andcomposed of material such that the impedance of this element is changedwhen the element becomes wet thereby causing an unbalance in the bridgecircuit and an output signal therefrom which is employed to initiate thearming operation of the mine. As the mine is dropped from the aircraft apull switch carried by the mine is actuated by a static line attachedthereto and to the aircraft or the switch may be actuated by hand, asthe case may be, thereby applying battery to an oscillator circuit toactuate the Wheatstone bridge aforesaid and to re move short circuitsfrom the electric igniters of the various explosive elements of theexplosively actuated switch mechanisms, as will more clearly appear asthe description proceeds.

In the event that the mine does not land in the water, the Wheatstonebridge remains balanced and a self destruction circuit is renderedeffective to fire a primer and thus destroy the vital components of themine at the expiration of a predetermined interval of time. Theunbalance of the Wheatstone bridge circuit, however, renders the selfdestruction circuit ineffective.

One of the objects of the present invention is to provide a shallowwater mine having new and improved Z,74,588 Patented Mar. 14, 1961 meansfor distinguishing between a launching of the mine in shallow water oron dry land, as the case may be.

Another object is to provide a shallow water mine having means effectiveto destroy the vital components of the mine a predetermined period oftime after the mine has been launched from an aircraft and landed onterra firma, in which means responsive to a wet condition thereof areemployed to prevent the destruction of such vital components when themine is planted in the water.

Still another object is the provision of a new and improved armingdevice for a shallow Water mine adapted it for launchingfr'om anaircraft in flight in which battery potential is operatively connectedthereto as the mine leaves the aircraft and the unbalance of a normallybalanced Wheatstone bridge having a water sensitive element in one ofthe arms thereof is employed toeffect the arming of the mine inpredetermined time delay relation after the mine has been planted withinthe water.

A still further object is the provision of a new and improved arming andfiring mechanism for a shallow water mine which discriminates betweenplanting in the water or on dry land, as the case may be, to arm themine when planted in water and to effectively destroy the mine mechanismwhen planted on land.

Still other objects, advantages and improvements will be apparent fromthe following description taken in connection with the accompanyingdrawing of which the single figure thereof illustrates the arming andself destructive features of a shallow water mine in accordance with apreferred embodiment of the invention.

Referring now to the drawing for a more complete understanding of theinvention, there is shown thereon in diagrammatic form a complete systemfor arming an aircraft planted shallow water mine when the mine landswithin water and the means for efiectively destroying the vital parts ofthe mine in predetermined time delayed relation with respect to theplanting thereof when the mine lands on dry terra firma.

The system comprises several more or less well known components enclosedwithin dashed outlines, each ofthe componentshaving a legend designatingthe particular component enclosed by the dashed outline correspondingthereto. These components comprise a high voltage power supply to whichbattery is applied by the operation of a pull switch S1 preferablysecured toa static line 13 and movable to an operated position as themine falls away from the aircraft. The operation of the pull switch alsoapplies battery potential both to an oscillater and signal amplifier andremoves a short circuit from each of three explosive elements, theoperation of which will be more clearly apparent as the descriptionproceeds.

The water sensing element comprises a Wheatstone bridge supplied withalternating current from the oscillater, the bridge circuit having inone arm thereof a transducer 14 composed of barium titanate in a drycondition. The Wheatstone brigde is initially balanced such that nooutput signal is obtained therefrom when the transducer is dry. Thetransducer element is carried. by the mine in. suchvmanner. that itbecomes wet when the mine is plantedwithin the water thereby changingthe impedance thereof and causing an output signal to be generated bythe Wheatstone bridge. The Wheatstone bridge and transducer element thuscomprise a water discriminating device which is effective to apply analternating current signal to the output thereof only when thetransducer element has become wet. The output of the bridge is connectedto a signal amplifier circuit comprising a plurality of transistors foramplifying the signal received from the, Wheatstone bridge when the minehas been planted within the water.

In the event that the mine is planted out of water, no bridge outputvoltage is obtained by reason of the balanced condition of the bridge.Under these conditions the high voltage power supply charges condenserC1 in the self. destruction circuit through resistance R1 connected;thereto. The resistance R1 and the capacity of condenser C1 aresufficiently large such that a time delay of substantially thirtyminutes is required for the voltage of the condenser C1 to build up to avalue sufficient to break down diode D1. When this occurs the selfdestruction primer 15 is operated by dischargecurrent from condenser C1thereby firing an explosion charge, not shown, and destroying the vitalmine components.

In the event that the mine is planted within water, a bridge outputvoltage is obtained. 'This voltage is amplified and rectified by theamplifier and destructor control circuits. The rectified A.-C. voltageso obtained is employed to perform three dififerent operations asfollows: after a delay of approximately ten minutes, condenser C2 ischarged through resistor R2 sufliciently to cause diode D2 to breakdown. When this occurs the discharge current from condenser C2 flowsthrough the primer 16 causing primer 16 to operate and remove a lockfrom a movable arming member 20 having a length of explosive traincarried thereby. The operation of primer 16 also closes all of thecontacts of explosively actuated switch S2. The closure of contacts 17of switch S2 completes an operating circuit to primer 18 whereby primer18 is operated when diode D3 is triggered at the expiration of anadditional predetermined period of time. This additional delay may be ofthe order of two hours during which condenser C3 has been chargingthrough resistor R3 to a potential sufiicient to break down or triggerdiode D3 at the completion of this additional delay period. When thisoccurs the discharge current of condenser C3 through primer 18 causesthe primer 18 to operate and align an explosive train within the armingmember 20 of the mine firing mechanism.

Switch S2 at contacts 19 thereof closes a circuit to set an arming clockinto operation. The arming clock per se forms no part of the presentinvention and may be of any type suitable for the purpose such forexample as the normally barred clock-work disclosed in Patent No.913,524 for Submarine Mine which issued February 23, 1909, to K. 0.Leon, in which a pair of contacts are closed in time delayed relationfollowing energization of the electromagnet M. When the clock hascompleted its arming cycle and the explosive train has been aligned byoperation of primer 18 the mine is in an armed condition. The mine isexploded by a firing mechanism of any well known type suitable forclosing a firing circuit to detonator 21 by way of closed contacts 22 ofswitch S2. Contacts 23 and 24 of switch S2 may be employedadvantageously to apply battery to the firing mechanism of the mine andclose a mine sterilizing circuit thereto respectively in the event thata sterilizing circuit is employed.

The unlocking and explosive train aligningvmechanism of arming member 20controlled by primers 16 and 18 respectively may be of any type suitablefor the purpose such, for example, as the mechanism disclosed andclaimed in the copending application of Herbert E.

Ruehlemann et al., Serial No. 577,617, filed April 11, 1956, for BombFuze and designated Arming Member on the single figure of the drawing,the control connections to primers 16 and 18 being shown by dashed linesrespectively.

The third operation performed by the amplifier and the destructioncontrol circuit is to provide a bucking or opposing voltage to the selfdestruction circuit. This is achieved by the circuit arrangementdisclosedin which the voltage obtained from the amplifier and destructorcontrol circuit when the mine lands in water is applied to condenser C4by way of rectifier 25 and to resistor 26 in parallel with condenser C4,the rectifier 25 being so connected that the voltage of condenser C4 isin opposing relation with respect to the voltage of condenser C1 andinsufficient to fire diode D1. With this arrangement the condenser C1,even though charged to its normal voltage at the end of the thirtyminute self destruction period is insufficient to trigger diode D1 'forthe reason that the voltage across diode D1 is the difierential voltagebetween the voltages on condensers C1 and C4. The diode D1 thus does notbreak down and cause destruction of the critical components of the minein the event that the mine lands within the Water. The voltage ofcondenser C4, however, is sufficient to cause operation of diodes D2 andD3 in the order named.

From the foregoing it is ,clearly apparent thatthere has been provided awater discriminating arming and self destruction circuit for a shallowwater mine in which the water sensing element comprises a balancedWheatstone bridge having a barium titanate element disposed within onearm thereof and adapted to cause bridge unbalance when the bariumtitanate element becomes wet and the impedance thereof is thus changed.The bridge output voltage is amplified and rectified, the amplified andrectified voltage being employed to unlock a normally locked armingmember having an explosive train carried thereby and simultaneouslytherewith close a plurality of control circuit contacts. At theexpiration of an additional predetermined period of time a second primer18 is operated to cause the arming member to be moved forcibly to anarmed position in which an explosive train is in alignment with thedetonator 21 and the usual booster charge of the mine. Normal firing ofthe mine is achieved in any well known manner, the firing circuitthereof including a pair of contacts 22 on the switch S2.

Should the mine land on the beach out of the water or elsewhere in suchmanner that the barium titanate transducer element remains in a drycondition, a slowly charging condenser C1 connected to the high voltagepower supply is charged to a potential sufificient to trigger diode D1and operate the electroresponsive primer 15 thereby to destroy the vitalcomponents of the mine and thus render identification thereofimpossible.

The mine for which the present circuit is well suited may advantageouslybe of the type adapted for launching from an aircraft in which thestatic line usually employed with such launching is secured at one endthereof to a pull switch whereby battery is applied to the circuits atthe. time the mine leaves the aircraft and a short circuit is removedfrom each of the unlocking, aligning and self destruction primersrespectively as the pull switch is operated.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. An arming and self destruction circuit for a shallow water mineadapted to be laid by an aircraft in flight, comprising a source ofelectrical energy, means operable as the mine falls away from theaircraftfor connecting the circuit to said source of energy, anoscillator, means operatively connecting said oscillator to a normallybalanced Wheatstone bridge, a barium titanate transducer arranged in oneof the arms of said bridge for destroying the balance thereof as thetransducer becomes Wet and thereby providing a bridge output signal,means for rectifying and amplifying said signal, a condenser connectedto: be charged by said rectified and amplified signal, a first diode,means operatively connecting said diode to the condenser whereby thediode is triggered when the charge on the condenser hasreached apredetermined value, a primer connected to the diode for operation bythe charge of the condenser as the diode is fired, and a normally lookedarming member carrying a length of explosive train and movable from aninitial safe position to an armed position, said primer being adapted tounlock said arming member as the primer operates.

2. An arming and self destruction device for an aircraft laid shallowWater mine comprising a source of electrical power, a switch operativelyconnected to the aircraft for establishing a circuit connection betweenthe device and said source of power, an initially balanced Wheatstonebridge, a barium titanate transducer included in one of the arms of saidbridge and adapted to destroy the balance thereof as the transducerbecomes wet and thus produces an output bridge signal, amplifying meansfor said signal, rectifying means connected to the output of saidamplifying means, a storage condenser having a resistance in paralleltherewith connected to said rectifying means and chargeable thereby tothe voltage of said amplified and rectified signal, a second condenserhaving a resistance in series therewith connected to the terminals ofsaid storage condenser and chargeable in time delayed relation withrespect to the time of charging said storage condenser, a diodeconnected to said second condenser in a manner to be fired when thecharge on the second condenser is sufiicient to break down the diode, aprimer in series With the diode and said second condenser and adapted tobe fired by discharge current of the second condenser through the diode,an explosive actuated switch operable by the primer as the primer isfired, said switch having a plurality of normally open pairs of contactsmovable to circuit closing position as the switch is operated, a thirdcondenser and a third resistance connected in parallel therewith and tosaid storage condenser, the time constants of said third condenser andresistance being such as to cause the third condenser to be charged at aslower rate than the rate of charge of the second condenser, a seconddiode connected to said third condenser and adapted to be fired therebywhen the charge on the third condenser has increased to a predeterminedvalue, a second primer connected to said second diode and operable bythe dis charge current of said third condenser as the second diode isfired, a movable arming member, and means for moving said arming memberto an armed position in response to the operation of the said secondprimer.

3. A device according to claim 2 including a fourth condenser and afourth resistor connected thereto through which the fourth condenser ischarged, a high voltage power supply, means including a plurality ofelectrical connections for establishing a charging circuit between saidfourth condenser and the power supply, a third diode operativelyconnected to said fourth condenser and adapted to be fired when thecharge on the condenser has increased to a firing potential at theexpiration of a prolonged period of time controlled by the fourthresistor and the capacity of the fourth condenser, and a third primeroperable by discharge current from the fourth condenser as the thirddiode is fired for causing destruction of the components of the mine.

4. A device according to claim 3 in which said fourth condenser andstorage condenser are connected in polarity opposition whereby the thirddiode is not fired when the storage condenser is charged in response toa signal received from said signal amplifying and rectifying means.

5. An arming and self destructive device for an aircraft launchedshallow water marine mine comprising a normally balanced Wheatstonebridge having a Water sensitive element in one arm thereof fordestroying the balance of the bridge as the element becomes wet andeffecting a bridge output signal, signal amplifying and rectifying meansconnected to the output of said bridge, a storage condenser connected tothe output of said signal amplifying and rectifying means and chargeablethereby, means including a pair of diodes connected to said condenserfor arming the mine in response to a signal received from the condenser,means including a third diode for causing self-destruction of the minein predetermined time delayed relation with respect to the launchingthereof when no signal is received from said Wheatstone bridge, andmeans for rendering said last named diode ineifective to causedestruction of the mine when a signal is received from the Wheatstonebridge.

6. A device according to claim 5 in which the diodes of said pair ofdiodes operate in predetermined order of succession and the time ofoperation of the third diode is greater than the time of operation ofthe first of said pair of diodes and less than the time of operation ofthe second of said pair of diodes.

7. A device according to claim 6 including an explm sively actuatedswitch, means including a primer connected to the first of said pair ofdiodes for operating said switch as the primer is fired in response tothe breakdown of the first diode, a second primer operatively connectedto the second diode of said pair of diodes and adapted to be fired asthe second diode breaks down, and means including a pair of normallyopen contacts on said switch for operatively connecting the secondprimer to said second diode as the switch operates.

References Cited in the file of this patent UNITED STATES PATENTS2,574,261 Hagan Nov. 6, 1951

